1. Field of the Invention
The invention relates to data processing systems and more particularly to a method and apparatus for communicating among a plurality of network nodes connected to the hub of a local area network.
2. Description of the Related Art
A Local Area Network, or LAN, is a data communications system which allows a number of independent devices to communicate with each other within a moderately sized geographical area. The term LAN is used to describe networks in which most of the processing tasks are performed by a workstation such as a personal computer rather than by shared resources.
A LAN node consists of a desktop workstation which performs processing tasks and serves as the user's interface to the network. A wiring system connects the workstations together, and a software operating system handles the execution of tasks on the network.
The configuration of the various pieces of the network is referred to as the topology. In a star topology, such as that defined in the IEEE 802.3 10 base-T network standard or the 100 Mbps EtherNet based on a star topology, the switching control is at the center of the network. All of the attached devices, the individual workstations, shared peripherals, and storage devices, are on individual links directly connected to the center of the star. In the star configuration, all of these devices communicate with each other through the center which receives signals and transmits them out to their appropriate destinations.
Star topologies have the advantage that the workstations can be placed at a considerable distance from the center of the star. In the star configuration the center of the star is involved in all of the communication signals. In a bus topology, communications messages have no central controller. Each device attempts to send signals and enter onto the bus when it needs to. If some other device tries to enter at the same time, contention occurs. To avoid interference (collision) between two competing signals, bus networks have signaling protocols that allow access to the bus by only one device at a time. The more traffic a network has, the more likely it is that a contention will occur. Consequently, the performance of a bus network is degraded if it is overloaded.
It is an object of the present invention to provide a hub for a star local area network that increases the link throughput by providing a means for reducing the number of collisions and the collision penalty when collisions do occur.